OBJECTIVES: Identifying cardiac surgical patients at risk of requiring red blood cell (RBC) transfusion is crucial for optimizing their outcome. We critically appraised prognostic models preoperatively predicting perioperative exposure to RBC transfusion in adult cardiac surgery and summarized model performance. METHODS: Design: Systematic review and meta-analysis. STUDY ELIGIBILITY CRITERIA: Studies developing and/or externally validating models preoperatively predicting perioperative RBC transfusion in adult cardiac surgery. Information sources MEDLINE, CENTRAL & CDSR, Embase, Transfusion Evidence Library, Web of Science, Scopus, ClinicalTrials.gov, and WHO ICTRP. Risk of bias and applicability: Quality of reporting was assessed with the Transparent Reporting of studies on prediction models for Individual Prognosis or Diagnosis adherence form, and risk of bias and applicability with the Prediction model Risk of Bias ASsessment Tool. SYNTHESIS METHODS: Random-effects meta-analyses of concordance-statistics and total observed:expected ratios for models externally validated ≥5 times. RESULTS: Nine model development, and 27 external validation studies were included. The average TRIPOD adherence score was 66.4% (range 44.1%-85.2%). All studies but 1 were rated high risk of bias. For TRUST and TRACK, the only models externally validated ≥5 times, summary c-statistics were 0.74 (95% CI: 0.65-0.84
6 contributing studies) and 0.72 (95% CI: 0.68-0.75
5 contributing studies) respectively, and summary total observed:expected ratios were 0.86 (95% CI: 0.71-1.05
5 contributing studies) and 0.94 (95% CI: 0.74-1.19
5 contributing studies), respectively. Considerable heterogeneity was observed in all meta-analyses. DISCUSSION: Future high quality external validation and model updating studies which strictly adhere to reporting guidelines, are warranted.